The Pagan Pantheon has a large number of Gods and Goddesses collected from several cultures. It's best to start learning about them by choosing a few from the most well known cultures. After some study, you will likely feel drawn to a particular group of god/desses, and you should continue to learn as much as possible about your chosen deities.
Many pagans never choose any one particular pantheon. Rather, they study several different pantheons, choosing god/desses that they feel are appropriate to the work they are doing. There are also groups which believe that all god/desses are aspects of a single unknowable being. These groups will often call upon the God and the Goddess.
The amount of time it takes to find your particular deity will vary, but it rarely happens instantly. You will probably go through several "not quite right" choices before you find the right one. Remember that a God/dess is shaped by the culture that worships it; the Norse God of the Lightning (Thor) is very different from the Greek God of the Lightning (Zeus). Knowing this, it makes sense to look at each culture separately. Lets start by looking at a few important gods from each culture.
Many pantheons are difficult to understand as they originally were for two major reasons. First, many of the groups that we look at today saw themselves not as a single unit, but as collections of smaller groups. For example, we will discuss the Ancient Greek Pantheon, but there was no "Greece" in that time. Rather, there was a collection of smaller countries loyal primarily to themselves (Athens, Sparta, Crete, etc). They were less like the States of the USA, and more like the countries of Europe prior to the European Union.
The second reason it is difficult to study the ancient pantheons is that there is seldom a record of what the original people believed. Instead, there are only the records of the peoples who conquered the original believers. For example, most of our knowledge of the Greek and Celtic Mythos come from the records of their Ancient Roman conquerors.
That being said, for most pagans it is enough to know the essence of a deity. Our interest is less in what people needed thousands of years ago, and more on how the God/desses react to us today. In many cases (in my experience) there have been subtle shifts in what the God/desses represent - and this is a more appropriate for the issues we face today. Remember, culture shapes belief, and belief shapes reality - even the God/desses.
Ancient Greek Gods and Goddesses are were much like the people they ruled. The were emotional and interacted with each other much like the ancient Greek upper classes. The took offense when insulted, and occasionally would elevate a mortal into their ranks. They also frequently interacted with their followers, but never let themselves be thought of as equals. When you needed help from the gods, you petitioned them, bribed them, or sought the help of one of their underlings (that is, their priests). The god/desses listed below have their Roman name listed after them for easy reference.
This is my favorite mythos, so there may be more entries than with other mythos on this page.
Zeus (Jupiter) - King of the Gods, rules the sky, storms rain, lightning
Aphrodite (Venus) - Goddess of love, lust, and beauty
Hera (Juno) - Goddess of marriage, women and childbirth, also jealousy
Dionysus (Bacchus) - God of Wine, parties, festivals, and dance. Also represents the beneficial and social virtues of drinking
Hades (Pluto) - King of the Underworld, death, and wealth
Persephone (Proserpina) - Goddess of the seasons, Queen of the Underworld, Goddess of rebirth and reincarnation [modern]
Demeter (Ceres) - Goddess of grain, harvest, mother or alternate form of Persephone
Eris (Discordia) - Goddess of strife [original] or chaos [modern]
Hecate (Trivia) - childbirth, nurturing the young, crossroads, magic and witchcraft, vengeance, judgment and justice
Rhea (Cybele) - Not a "God", but a "Titan", (The "Gods" who gave birth to the Gods) The Mother of the Gods, honored as giving birth to all the God/desses of the Greeks
Gaia (Gaea, Terra Mater, Tellus) - The Earth itself, the Roman name "Terra Mater" literally means "Earth Mother"
Ancient Egypt is known through a few references in Roman and Hebrew history, but mostly through Hieroglyphics found in their monuments. The Gods and Goddesses of Ancient Egypt were reached through very controlled channels: The people spoke to priests who were answerable to the Pharaoh. The Pharaoh himself was seen as the earthly incarnation of the God Ra. Because of this system, the Egyptian mythos is heavily favored by many Ceremonial Magicians.
Isis - Goddess of motherhood, magic, fertility; from Isis all thing were born
Ra - God of the Sun, sky, creation, leadership, power
Hathor - Goddess of love, motherhood, joy, music, dance, foreign lands and fertility
Bast or Bastet - Goddess of cats, protection, stealth, independence
The Norse (Viking or Northern Germanic) Mythos is unusual in that it survived as written by its own people. Unfortunately, most of this writing was either created by or transcribed by Christian scholars, who couldn't help but add their own bias. The Norse gods were not the distant nobles of Greek myth, but simply the people who ran the next life. They fought the same types of wars and had many of the same challenges as their followers, and they would eventually die. Norse Gods and Goddesses are not prayed to, but rather invoked and channeled.
Odin - One-eyed Ruler of the Gods, called the All-Seeing, God of wisdom, fighting, victory, magic, death, poetry, and divination
Thor - God of Thunder, The Hammer of Thor is one of the most common symbols used by Pagan following the Norse mythos.
Tyr - God of single combat, victory, heroic glory, justice, sacrifice for the greater good [modern]. Tyr lost one of his hands so that Fenris the wolf could be bound, preventing it from eating the sun.
Freya - Goddess of love, beauty, fertility, childbirth, magic, prophesy, wealth
Valkyries - Goddesses who collect the souls of those who fall in battle
The Celtic mythos can refer to the Welsh mythos, the Irish mythos, the Scottish mythos, or even to any number of "Lost" Celtic tribes (those that were absorbed into the Roman Empire). More than any other on this page, the Celtic mythos are difficult to trace to their original meanings. The ancient Celts left little in the way of monuments and writings (megalithic monuments like Stonehenge non-withstanding). Many Traditions call on the Celtic God/desses without regard to which culture it originated with, but each culture is distinct. I have included the root culture for each listing for those interested in learning more.
Rhiannon (Welsh) - Goddess of forgiveness, steadfastness, motherhood, rebirth
Ariwan (Welsh) - Lord of the Underworld, God of Death
Morrigan (Irish) - Sometimes a Triple Goddess, associated with sovereignty, death, and war
Meave or Medb (Irish) - Queen to several husbands in Irish mythos, marriage, women's power
Lugh (Irish) - The All Skilled, God of poetry, music, art, war, skillfulness, and leadership
Brigid (Irish) - Often a Triple Goddess, Goddess of poetry, healing, creation, wisdom, duality
There are many God/desses and mythos that I am simply unfamiliar with. There are also some deities that simply don't fit into the larger categories above. The brief list below might give you some ideas for beginning your own investigations.
The God and Goddess of Wicca (Modern Wiccan) - The God and Goddess of Wicca are often seen as the combined incarnations of all God/desses of all the pantheons of the world. The God and Goddess together create the story behind the Wheel of the Year.
Guan yin or Kuan Yin (Chinese Buddhist)
Inannna (Sumerian)The Urban Pagan › Gods and Goddesses